Although it is generally agreed that arterial wall stiffening increases during aging, determinants of this aging associated vascular process remain largely unknown and little longitudinal data is available. This is, in part, due to lack of a measurement technique for arterial wall stiffening with sufficient precision to detect short-term change. The applicants propose to develop an image processing system to obtain precise arterial diameter and intima- media thickness measurements from B-model ultrasound images that can be used to compute commonly used stiffness indices including Pearson's elastic modulus, Young's modulus, Hirai's stiffness indicator Beta, distensibility and elasticity. They propose to implement a computer work- station that will allow view matching to be carried out from extended sequences of digitized images rather than from video images. This system will provide the capability to use split screen display of two examinations and to sequence through images at variable rates up to 10 to 20 times faster than with VCR's. The PI and his collaborators will determine the intra-and-inter-sonographer variability of the stiffness measurements from replicate common carotid artery ultrasound scans of 100 subjects, ages 40 to 80 years, imaged twice 1 to 2 weeks apart by 2 ultra- sonographers. In addition, they will compare the stiffness indices calculated with brachial pulse pressure measured by oscillatory with carotid pulse pressure measured by applanation tonometry. Long-term goals will be to apply this new image processing technology to two current funded randomized carotid ultrasound trials of vitamin E supplementation and 17 -estradiol replacement therapy in healthy 40 to 80 year olds. These goals will demonstrate how this new image processing technology can be easily deployed in large-scale epidemiological studies and clinical trials to obtain information on the risk factors for, as well as the prevention and reversal of, vascular stiffness in aging.